1. Field of the Invention
The present invention relates to a water based ink composition for a writing instrument which sheds fragrance in writing and which imparts faint fragrance as well to drawn lines.
2. Description of the Related Art
In general, perfumes are oil-soluble, and an emulsifier or a dispersant which forms protective colloid is required in order to emulsify or disperse them in water. Water-soluble resins or surfactants are used as the protective colloid described above. In almost all water-soluble resins, however, use of a necessary and sufficient amount of a resin required for dispersing a perfume raises a viscosity of the liquid and makes it inadequate for an ink for a writing instrument.
On the other hand, an emulsion which is prepared using a surfactant in an amount enough for emulsifying a perfume in a stable state is reduced in the surface tension to a large extent, so that an ink prepared using the emulsion has the practical problem that drawn lines are liable to cause feathering. Further, an ink prepared merely emulsifying and dispersing a perfume by the method described above involves the problem that fragrance is shed immediately after writing but the fragrance is lost soon thereafter and can not be retained for long time (no durability).
Those which have so far been known as ink compositions for a writing instrument containing a perfume shedding fragrance in writing include, for example, inks for a ball point pen comprising dyes, resins and organic solvents, wherein a perfume having a compatibility with the above inks is added (Japanese Patent Application Laid-Open No. Sho 56-81377), perfume-containing water based inks blended with a perfume, maltosyl cyclodextrin (MCD), a colorant and water (Japanese Patent Application Laid-Open No. Sho 63-223078) and water based ink compositions for a writing instrument comprising a colorant, a perfume, a partially sulfonated polyester resin and water (Japanese Patent Application Laid-Open No. Hei 8-283645).
However, the ink composition disclosed in Japanese Patent Application Laid-Open No. Sho 56-81377 involves the problem that even if adding a perfume having compatibility, feathering is caused on a paper surface in writing. Also, the ink composition disclosed in Japanese Patent Application Laid-Open No. Sho 63-223078 is prepared by including a perfume in MCD and adding the above inclusion compound to a water based ink, and therefore the perfume contained in this water based ink tends to easily be separated with the passage of time, particularly with the passage of time at a high temperature, so that the ink composition involves problems in dispersibility of the perfume and durability of fragrance. Further, the ink composition disclosed in Japanese Patent Application Laid-Open No. Hei 8-283645 involves the problem that fragrance is shed immediately after writing but the fragrance is lost thereafter and can not be retained for long time (no durability).
The present invention intends to solve the problems of the conventional techniques described above, and an object thereof is to provide a water based ink composition for a writing instrument which is less liable to cause feathering and has durability of fragrance and in which a perfume is dispersed and retained in an aqueous medium in a stable state.
Intensive researches repeated by the present inventors regarding the problems of the conventional techniques described above have resulted in successfully obtaining a water based ink composition for a writing instrument which meets the object described above by adding a specific ink component to a water based ink composition for a writing instrument comprising a colorant and a perfume, and thus the present invention has been completed.
That is, the water based ink composition for a writing instrument of the present invention contains at least one selected from the group consisting of a polyoxyethylene alkyl ether phosphate and salts thereof and further contains a colorant, a perfume and water.